you might think about putting the 45 degree box on. I picked up a bunch of car magazines that were free on craigslist and most were from the 90's. There was a Street Power magazine from 97 that had a hop up article on a 90 300zx twin turbo. The part that caught my attention was replacing the stock air box which has the same setup as the airbox on our cars. The inlet to the maf is in a corner with the wall very close and it is hard for the air to travel up and make that tight turn into the maf. They were seeing an 18 horse increase by getting rid of the stock box which is a huge restriction. Why Subaru put the shrouded airbox on the turbo cars and the 45 degree box on na cars beats me. I would think the 45 degree box should be worth at least 10 horses on our cars going by their results. The guy that was doing these kits was Jim Wolf technologies who I have no idea if he is still in business, but when I saw the pictures of the airbox I said that looks really familiar.

Last edited by wtdash on Fri Feb 21, 2014 5:20 pm, edited 1 time in total.

jefferson

Post subject: Re: If you are still running the stock airbox,

Posted: Fri Feb 21, 2014 4:12 pm

Third Gear

Joined: Sat Dec 16, 2006 4:41 am

Posts: 725

Location: Parkville, Mo.

That article is where I got the idea. I wish they had gone on and tested the airbox. It would have been good to have some cold hard facts, but all you have to do is look at the two and you will see that the 45 degree one is able to flow much more air because the maf entrance is not shrouded by the walls of the box and the air doesn't have to make two 90 degree turns.

Josh hosted some pictures of my airbox setup. If you search for 45 degree airbox you should come up with the threads with the pictures. Wish I was better at this computer stuff so I could link it here.

I'd be curious to see what changing to the 45 deg airbox does for the pressure drop. I've thought about the way the airbox is shaped and I question whether Subaru did it intentionally to create an area of low pressure just before the MAF to possibly help the air flow more evenly through the MAF. That may just be a hair brain idea though....

I converted to the 45 degree airbox as well and am running a custom made intake pipe. It's kind of a bitch to remove the airbox/intake pipe, but works well.

Yes, that is an extra inlet "feeder" pipe to the bottom side of the airbox. I don't know if it really makes a difference, but I had added it probably around 2002 and decided to leave it there when I changed air boxes.

That is the one downside to this setup in that there isn't enough give in the system to take things apart easily. If I would start at the rubber elbow where it connects to the turbo I think it would be much easier. I always start in the middle and end up fighting things.

Another thing I did to improve the flow was to use a thin wall tube on the inside of the 90 degree rubber connector on top the turbo. The sleeve is on the inside of the ribs so they can still flex, but now they don't impair the flow of air. There is a lip that keeps the thing in place.

I don't have any pictures of it. It was easy to measure for the length and od. The lip is at 90 degrees so it is shaped kind of like a top hat and it rests on the edge right before the ribs. I had a metal spinning shop do it for me. My only concern is if the thing digs into the rubber when things are flexing. Everything looked fine the last time I checked.